San Francisco Walking Tours - From History to Ghosts

While it's said that "nobody walks in L.A.," it's known that everyone walks in San Francisco. Having been a resident and frequent visitor to San Francisco, I can tell you that the very idea of walking in the City has always seemed odd to me. Let's face it; it's not the flattest town in which to walk. Yet, that's what everyone does. Walk, and huff and puff, and walk some more. There's just something about San Francisco that makes you want to step outside your hotel and walk. Perhaps it has something to do with the many different fascinating neighborhoods and buildings that compel people to slow down and take it all in.

If you're planning a vacation or holiday to San Francisco one of the best ways to actually experience the city is to take a walking tour. And, when it comes to walking tours, both free and fee-required, San Francisco has more than its share (it must have taken some from L.A.).

Free Walking Tours

First, let's begin with the free tours offered by San Francisco City Guides, a non-profit organization of more than 200 trained volunteers who lead free walking tours in San Francisco (donations, of course, are gladly accepted). If you visit their website, sfcityguides.org, you'll notice an interesting array of free walking tours offered every day of the week, tours like "1906 Earthquake and Fire," "Art Deco Marina," "Chinatown," "City Hall," "Downtown Deco," "Financial District" and "Gold Coast Architecture." A few of the more interesting walks include:

"Bawdy & Naughty"

This downtown two-block walk explores the arrival of "professional" women in San Francisco during the Gold Rush. And, no, we're not talking about women doctors or lawyers.

"Castro: Tales of the Village"

The Castro area in San Francisco is a predominately gay area of town. But, it wasn't always that way. This tour explores the early years of the Castro.

"Coit Tower Murals"

This tour takes visitors to Coit Tower on Telegraph Hill to view the Murals created by some of California's leading artists of the 30s depicting life in the Great Depression. The murals are definitely worth seeing, either as a tour group or on your own. San Francisco City Guides say their tour shows you some murals not shown to the general public, so I recommend you consider the tour for this San Francisco landmark.

"Ghost Walks"

Here are a couple fun walking tours. The "Ghost Walk at City Hall" and the "Ghost Walk at the Palace" are held in October only, and explore, what else, ghostly occurrences.

The tours typically begin in easy to identify and very public places and most of them even meet near access to public transportation in order to accommodate visitors coming from other areas of the city.

Fee-Required Tours:

While you do have plenty of opportunity for free walking tours, you might also consider some of the fee-required tours. One such fee-required tour is Hobnob Tours, a walking tour of Nob Hill, often times referred to as Snob Hill due to the number of wealthy people who live there. This two-hour tour costs $30 and takes you to an elegant ballroom where Tony Bennett belted out "I Left My Heart in San Francisco," through spectacular Grace Cathedral, through Huntington Park, with a cable car ride up Nob Hill. There is an optional breakfast, lunch or high tea at added cost. You can call for more information at 866-851-1123.

Another Fee-required tour is a tour of Chinatown which includes a visit to a fortune cookie factory and herbal pharmacy, as well as a hosted 10-course Dim Sum lunch at a Chinatown restaurant. The tour-only price is $28 for adults, $15 for children 6-17. With the added Dim Sum lunch the price is $40 for adults, $27 for children. You can call for reservations at 415-982-8839.

Whichever tour you decide to take you will probably leave you feeling satisfied, either with a greater insight to San Francisco, or with great Dim Sum.

Shari Hearn is a writer and creator of Top Vacation Spots, where you can learn about such things as Canary Island Holidays.

 

CCNP certification is getting a new look at the end of 2006. The BSCI and BCMSN exams are being updated, and the CIT and BCRAN exams are being retired. Let's take a look at what to expect from the new BSCI exam.

According to Cisco's exam blueprint - admittedly a very broad blueprint at this time - the major new topics are IP version 6 (IPv6) and multicasting. The addition of these two topics will make an already demanding Cisco certification exam that much tougher, but this is a great change for the exam and for the candidate. IPv6 is just going to become more and more prevalent in today's networks, and multicasting is as well.

Multicasting for the Cisco CCNP BSCI exam is going to go far beyond what you learned about it in your CCNA studies. For the new BSCI exam, you'll need to know the different methods of creating multicast groups as well as assigning members to them. This material was previously limited to CCIE-level books, and while I don't look for the questions to be as hard as the CCIE written exam, multicasting is not an easy topic and should not be taken lightly by the CCNP candidate in 2007.

One major CCNP exam topic that isn't going anywhere is BGP. The Border Gateway Protocol has been a big part of previous BSCI exams, and that looks to continue.

If you're pursuing your CCNP certification in 2007, be sure to monitor Cisco's website for additions to the CCNP blueprint. It's obvious that Cisco has raised the bar for CCNP certification, and earning this important Cisco certification will in turn raise your market value and networking knowledge like never before. Watch for future tutorials examining the other three new CCNP exams!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of over 100 free certification exam tutorials, including Cisco CCNA certification test prep articles. His exclusive Cisco CCNA study guide and Cisco CCNA training is also available!

Visit his blog and sign up for Cisco Certification Central, a daily newsletter packed with CCNA, Network+, Security+, A+, and CCNP certification exam practice questions! A free 7-part course, ?How To Pass The CCNA?, is also available, and you can attend an in-person or online CCNA boot camp with The Bryant Advantage!

 

San Francisco Gets Serious About Arts Education

The Arts Education Master Plan

September 28 was the beginning of a new era for arts education in San Francisco schools. The San Francisco Unified School district and the City are partnering on a historic effort to bring back the arts for all students. The Arts Education Master Plan will revitalize the education of San Francisco?s young citizens by capturing the diverse cultural and artistic energy of a city that is internationally renowned for its love of the arts.

At 10:30 a.m. at the San Francisco Performing Arts Library and Museum, Mayor Gavin Newsom, SFUSD?s Interim Superintendent Gwen Chan, and SF Arts Commission President P.J. Johnston joined members of the Board of Supervisors and SFUSD Board of Education, arts providers from across the city and students from Lowell High School, Claire Lilienthal and George Washington Carver Academic Elementary Schools in celebration of the Arts Education Master Plan.

"This master plan is a living document that exemplifies the partnership between the City and the school district on arts education," said Mayor Newsom. "San Francisco's efforts are unprecedented - and over the next few months, we will witness 'order of magnitude' changes in the arts education that children receive," continued the Mayor.

The Arts Education Master Plan is San Francisco Unified School District's blueprint for integrating the arts into each student's daily curriculum. The Plan calls for a sequential, comprehensive arts education program that reflects the high quality of San Francisco's artistic landscape in the areas of dance, drama, music, visual arts and literary arts.
The guiding principle of this plan is that all students deserve both access to and equity in arts education and each school community, no matter the neighborhood or academic emphasis, will be called upon to embrace the notion that every student must be provided with the arts as an integral part of the academic day.

Interim Superintendent Gwen Chan said ?In San Francisco, we are committed to providing every student with a well-rounded education. For too many years, some students have not had opportunities to develop artistic literacy. Every school and every student will benefit from this plan.?

Community Involvement

The Master Plan reflects the views of more than 1,500 students, parents, teachers, administrators, arts providers, and civic and business leaders. Proposition H approved by San Francisco voters in 2004, became the catalyst, making the Arts Education Master Plan, completed in August 2006, a funded mandate. The extensive increase in arts education spending, programming, support and resources that the Plan recommends will be funded largely by Prop H funds. Additional funding, such as the new State funding for the arts, will be aligned to the Arts Education Master Plan.

The new plan will hopefully keep San Francisco school students in touch with the vibrant artistic community around them and help them to take advantage of the many enriching opportunities for art in the classroom and beyond. San Francisco schools are ready to implement the new curriculum program at all levels to ensure a consistent and fulfilling learning experience for all students. Students, parents, and teachers at San Francisco schools are confident that the Arts Education Master Plan will mark their community as one committed to continued arts education.

Stacy Andell is a staff writer for Schools K-12, providing free, in-depth reports on all U.S. public and private K-12 schools. For more information on San Francisco schools visit http://www.schoolsk-12.com/california/san-francisco/index.html

 

Cisco CCNP / BSCI Exam Tutorial: Ten IP Routing Details You Must Know!

To pass the BSCI exam and earn your CCNP, you've got to keep a lot of details in mind. It's easy to overlook the "simpler" protocols and services such as static routing and distance vector protocols. With this in mind, here's a quick review of some details you should know for success in the exam room and real-world networks!

When packets need to be routed, the routing table is parsed for the longest prefix match if multiple paths exist with the same prefix length, the route with the lowest AD is preferred. If there are still multiple valid paths, equal-cost load-sharing goes into effect.

The ip route command is used to create static routes the command ip route 0.0.0.0 0.0.0.0 < next-hop-IP or local exit interface> creates a default static route.

A static route with a next-hop IP address has an AD of one, while a static route with a local exit interface has an AD of zero.

A floating static route is a static route with an AD higher than that of the dynamic routing protocols running on the router, ensuring that the static route can only be used if the routing protocol goes down.

On-Demand Routing (ODR) is only appropriate in a hub-and-spoke network. The spokes effectively become stub routers. ODR uses Cisco Discovery Protocol (CDP) to send route information.

To propagate a default route with IP routing, use the ip default-network command. To do so with IP routing disabled, use ip default-gateway. You can also redistribute a static route into most protocols, but not IGRP. IGRP does not understand a static route to 0.0.0.0.

The ip helper-address command takes certain broadcasts and translates then into unicasts in order to allow the router to forward them. These default ports are:

TIME, port 37

TACACS, port 49

DNS, port 53

BOOTP/DHCP Server, port 67

BOOTP/DHCP Client, port 68

TFTP, port 69

NetBIOS name service, port 137

NetBIOS datagram services, port 138

To name other ports, use the ip forward-protocol command. To remove any of these ports from the default list, use the no ip forward-protocol command.

ICMP Router Discovery Protocol (IRDP) hosts hear multicast Hellos from routers, allowing host-router discovery. HSRP routers create a virtual router that hosts think is a real router. Both protocols help networks cut over to a functional router quickly when their primary router goes down.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Get your CCNA study guide from The Bryant Advantage!

Cisco CCNP / BCMSN Exam Tutorial: Changing The Active Router In HSRP

To pass the BCMSN exam and earn your CCNP certification, you've got to know HSRP inside and out. While the operation and basic commands of HSRP are pretty simple, there are some important details that are easily overlooked but are vital in getting HSRP to work the way you want it to. Let's take a look at using the priority command correctly on both the exam and in production networks.

A key value in the show standby command is the priority. The default is 100, and the router with the highest priority will be the primary HSRP router. We'll raise the default priority on R2 and see the results. R3 is currently the Active router and R2 the standby, so let's raise the priority on R2 and see what happens.

R2(config)#interface ethernet0

R2(config-if)#standby 5 priority 150

R2#show standby

Ethernet0 - Group 5

Local state is Standby, priority 150

Hellotime 4 sec, holdtime 12 sec

Next hello sent in 0.896

Virtual IP address is 172.12.23.10 configured

Active router is 172.12.23.3, priority 100 expires in 8.072

Standby router is local

1 state changes, last state change 00:14:24

R2 now has a higher priority, but R3 is still the active router. R2 will not take over as the HSRP primary until R3 goes down - OR the preempt option is configured on R2.

R2(config-if)#standby 5 priority 150 preempt

1d11h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Standby -> Active

R2#show standby

Ethernet0 - Group 5

Local state is Active, priority 150, may preempt

Hellotime 4 sec, holdtime 12 sec

Next hello sent in 1.844

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.3 expires in 10.204

Virtual mac address is 0000.0c07.ac05

2 state changes, last state change 00:00:13

In just a few seconds, a message appears that the local state has changed from standby to active. Show standby confirms that R2, the local router, is now the active router - the primary. R3 is now the standby. So if anyone tells you that you have to take a router down to change the Active router, they're wrong - you just have to use the preempt option on the standby priority command.

Another vital part of HSRP configurations is knowing how to change the MAC address of the virtual router, as well as interface tracking. We'll look at those features in the next part of my HSRP tutorial!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNP and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Pass your CCNP exam with The Bryant Advantage

Cisco CCNA Certification Exam Tutorial: ISDN Details You Must Know

CCNA exam success depends partially on knowing the details of ISDN, and there are plenty of them! To help you review for your CCNA exam, here are a few ISDN details that you must know on exam day. (They help in the real world, too - and there are still plenty of ISDN networks out there!

The Cisco-proprietary version of HDLC is the default encapsulation type for serial and ISDN interfaces.

R2#show interface serial0

Serial0 is up, line protocol is up

Hardware is HD64570

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255

Encapsulation HDLC, loopback not set, keepalive set (10 sec)

While there's only one D-channel in BRI, PRI (US) and PRI (EU), the bandwidth of that D-channel does vary from BRI to PRI. It's 16 kbps in BRI and 64 kbps in both PRI versions.

The global command isdn switch-type must be configured before you can even begin to have ISDN work. show isdn status will tell you whether or not you've done this correctly.

R2#show isdn status

**** No Global ISDN Switchtype currently defined ****

ISDN BRI0 interface

dsl 0, interface ISDN Switchtype = none

Layer 1 Status:

DEACTIVATED

Layer 2 Status:

Layer 2 NOT Activated

Layer 3 Status:

0 Active Layer 3 Call(s)

PAP allows passwords to be different; CHAP requires that they be the same.

PAP requires the "ppp pap sent-username" interface-level command. CHAP has no equivalent command.

Define interesting traffic with dialer-list and link that list to the interface with dialer-group.

R2#conf t

R2(config)#dialer-list 1 proto ip permit

R2(config)#int bri0

R2(config-if)#dialer-group 1

The dialer idle-timeout value is expressed in seconds, not minutes. (Even IOS Help isn't totally clear on this.)

R2(config)#int bri0

R2(config-if)#dialer-group 1

R2(config-if)#dialer idle-timeout ?

<1-2147483> Idle timeout before disconnecting a call

R2(config-if)#dialer idle-timeout 120

Dialer map maps a remote IP address to a remote phone number. You never dial the local router's phone number.

dialer load-threshold requires the ppp multilink command to be configured, and the value of dialer load-threshold is expressed as a ratio of 255, NOT 100. For example, if you want the second b-channel to come up when the first reaches 50% of capacity, the value to express with dialer load-threshold would be 50% of 255 - which equals 127.

R2(config)#int bri0

R2(config-if)#encap ppp

R2(config-if)#ppp multilink

R2(config-if)#dialer load-threshold ?

<1-255> Load threshold to place another call

Success on the CCNA exam depends on knowing the details. Keep studying, keep practicing on real Cisco routers and switches, keep a positive attitude, and you're on your way to CCNA exam success!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Get your CCNA study guide from The Bryant Advantage!

Cisco CCNP / BSCI Exam Tutorial: The Passive Interface Command And OSPF

To pass the BSCI exam and become a CCNP, you have to be aware of the proper use of passive interfaces. You learned about passive interfaces in your CCNA studies, but here we'll review the basic concept and clear up one misconception regarding passive interfaces and OSPF.

Configuring an interface as passive will still allow the interface to receive routing updates, but the interface will no longer transmit them. While the command itself would make you think this command will be applied at the interface level, that is not the case. Below, we'll configure ethernet0 as a RIP passive interface.

R1(config)#router rip

R1(config-router)#passive-interface ethernet0

Ethernet0 will no longer send RIP routing updates, but will accept them.

The passive interface concept is clear enough with RIP, IGRP, and EIGRP - all protocols that send routing update packets. But OSPF doesn't send routing update packets - OSPF sends link state advertisements. It's the inability of the passive interface command to stop LSAs that lead many to think that passive interfaces cannot be used with OSPF.

Even though OSPF does not sent "routing updates" in the form that RIP, IGRP, and EIGRP do, you can still configure an OSPF-enabled interface as passive in order to prevent OSPF traffic from exiting or entering that interface. No OSPF adjacency can be formed if one of the interfaces involved is a passive interface, and if you configure an OSPF-enabled interface as passive where an adjacency already exists, the adjacency will drop almost immediately.

Let's see that in action. R1 and R2 have an existing OSPF adjacency over their Ethernet interfaces. In an effort to reduce routing traffic, R1's e0 interface is configured as passive. The adjacency drops right away.

R1(config)#router ospf 1

R1(config-router)#passive-interface ethernet0

18:31:11: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on Ethernet0 from FULL to DOWN, Neighbor Down: Interface down or detached

Knowing how to use the passive interface command is a vital part of being a CCNP, and of being a master networker. Good luck to you in both of these pursuits!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage , home of free CCNA and CCNP tutorials! Pass the CCNA exam with Chris Bryant!

Cisco CCNP / BCMSN Exam Tutorial: BPDU Skew Detection

You may look at that feature's name and think, "What is a BPDU Skew, and why do I want to detect it?" What we're actually attempting to detect are BPDUs that aren't being relayed as quickly as they should be.

After the root bridge election, the root bridge transmits BPDUs, and the non-root switches relay that BPDU down the STP tree. This should happen quickly all around, since the root bridge will be sending a BPDU every two seconds by default ("hello time"), and the switches should relay the BDPUs fast enough so every switch is seeing a BPDU every two seconds.

That's in a perfect world, though, and there are plenty of imperfect networks out there! You may have a busy switch that can't spare the CPU to relay the BDPU quickly, or a BPDU may just simply be lost in transmission. That two-second hello time value doesn't give the switches much leeway, but we don't want the STP topology recalculated unnecessarily either.

BDPU Skew Detection is strictly a notification feature. Skew Detection will not take action to prevent STP recalculation when BDPUs are not being relayed quickly enough by the switches, but it will send a syslog message informing the network administrator of the problem. The amount of time between when the BDPU should have arrived and when it did arrive is referred to as "skew time" or "BPDU latency".

A busy CPU could quickly find itself overwhelmed if it had to send a syslog message for every BPDU delivery that's skewed. The syslog messages will be limited to one every 60 seconds, unless the "skew time" is at a critical level. In that case, the syslog message will be sent immediately with no one-per-minute limit.

And what is "critical", according to BDPU Skew Detection? Any value greater than 1/2 of the MaxAge value, making the critical skew time level 10 seconds or greater.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNP and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Pass your CCNP exam with The Bryant Advantage

Cisco CCNP / BSCI Exam Tutorial: Using The OSPF Command "Area Range"

Your BSCI and CCNP exam success depends on knowing the details, and one such detail is knowing the proper way to summarize routes in OSPF. Route summarization is not just a test of your binary conversion abilities, but knowing where and when to summarize routes. It will not surprise any CCNA or CCNP certification candidate that OSPF gives us the most options for route summarization, and therefore more details to know!

OSPF offers us two options for route summarization configurations. In a previous tutorial, we looked at the "summary-address" command, and today we'll look at the proper use of the "area range" command.

The "area range" command should be used on an Area Border Router (ABR) to summarize routes being advertised from one OSPF area to another. In this tutorial, R1 is acting as an ABR, with interfaces in both Area 0 and Area 1. Four loopbacks have been placed into R1's Area 1.

R1(config)#router ospf 1

R1(config-router)#network 12.0.0.0 0.255.255.255 a 1

R1(config-router)#network 13.0.0.0 0.255.255.255 a 1

R1(config-router)#network 14.0.0.0 0.255.255.255 a 1

R1(config-router)#network 15.0.0.0 0.255.255.255 a 1

The routing table of an OSPF neighbor, R2, shows all four routes.

R2#show ip route ospf

12.0.0.0/32 is subnetted, 1 subnets

O IA 12.12.12.12 [110/65] via 172.12.123.1, 00:18:52, Serial0

13.0.0.0/32 is subnetted, 1 subnets

O IA 13.13.13.13 [110/65] via 172.12.123.1, 00:18:42, Serial0

14.0.0.0/32 is subnetted, 1 subnets

O IA 14.14.14.14 [110/65] via 172.12.123.1, 00:18:32, Serial0

15.0.0.0/32 is subnetted, 1 subnets

O IA 15.15.15.15 [110/65] via 172.12.123.1, 00:18:32, Serial0

To keep the routing tables of downstream routers smaller but still have the desired IP connectivity, we can use the area range command on R1 to summarize these four routes. The key to keep in mind with the area range command is that the area number given in the command is the area containing the destinations, NOT the area that will receive the summary route.

R1(config)#router ospf 1

R1(config-router)#area 1 range 12.0.0.0 252.0.0.0

R2 now shows a single summary route that can be used to reach all four remote networks.

R2#show ip route ospf

O IA 12.0.0.0/6 [110/65] via 172.12.123.1, 00:00:21, Serial0

Interestingly enough, there's now an additional route in R1's routing table.

R1#show ip route ospf O 12.0.0.0/6 is a summary, 00:07:53, Null0

When you configure summary routes in OSPF, a route to null0 will be installed into the OSPF routing table of the router performing the summarization. This helps to prevent routing loops. Any packets destined for the routes that have been summarized will have a longer match in the routing table, and packets that do not match one of the summarized routes but do match the summary route will be dropped.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNP and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Pass your CCNP exam with The Bryant Advantage!

Cisco CCNP / BCMSN Exam Tutorial: Dynamic VLANs and VMPS

Knowledge of Dynamic VLANs and VMPS is important in your efforts to pass the BCMSN exam and earn your CCNP, and it's also a great skill to have for your networking career.

As a CCNA and CCNP candidate, you know how and why to configure static VLANs. Static VLANs can be a powerful tool for reducing unnecessary broadcast and multicast traffic, but if hosts are moved from one switch port to another, you've got to make those changes manually on the switch. With Dynamic VLANs, the changes are made - how else? - dynamically.

The actual configuration of dynamic VLANs is out of the scope of the BCMSN exam, but as a CCNP candidate you need to know the basics of VMPS - a VLAN Membership Policy Server.

Using VMPS results in port VLAN membership changes being performed dynamically, because the port's VLAN membership is decided by the source MAC address of the device connected to that port. (Yet another reason that the first value a switch looks at on an incoming frame is the source MAC address.)

In my home lab network, I've got a host connected to switch port fast0/1 that resides in VLAN 12. What if we had to move Host 1's connection to the switch to port 0/6? With static VLANs, we'd have to connect to the switch, configure the port as an access port, and then place the port into VLAN 12. With VMPS, the only thing we'd have to do is reconnect the cable to port 0/6, and the VMPS would dynamically place that port into VLAN 12.

I urge you to do additional reading regarding VMPS. Use your favorite search engine for the term configuring vmps and you'll quickly find some great official Cisco documentation on this topic.

To review, the VLAN membership of a host is decided by one of two factors. With static VLANs, the host's VLAN membership is the VLAN to which its switch port has been assigned. With dynamic VLANs, it is dependent upon the host's MAC address.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNP and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Get your CCNP with The Bryant Advantage!

Cisco CCNA Certification Exam: The OSI Model's Physical Layer

 

To pass your CCNA exam and earn this coveted certification, you've got to master the seven layers of the OSI model and what each layer does. For those of you taking the two-exam path, you can expect quite a few OSI model questions on the Intro exam. In this seven-part series, we'll spend some time taking a look at each of the OSI model layers, starting with the Physical layer.

Often, CCNA candidates ask if the OSI model has any practical uses for network administrators. I used to wonder the same thing, and I can now tell you that the answer is definitely yes!

The OSI model isn't something you want to memorize and then forget about, as using the OSI model gives you a structured approach for troubleshooting. Whenever a network device isn't working properly, I always say to "start at the physical layer". The Physical layer is Layer One of the OSI model, and this is where troubleshooting should always start. Is the device on? Is it properly connected? If everything is fine at Layer One, you just move up to Layer Two, and continue in this structured fashion until the problem is identified.

The Physical layer is the layer at which bits are transmitted over the physical media. There is no routing or switching going on at this layer. The data has been broken down into more manageable pieces until the data takes the form of ones and zeroes at the Physical layer.

Even though there's no routing or switching at the Physical layer, CCNA candidates should be familiar with a couple of network devices that work at Layer One. A repeater is a device that regenerates an electrical signal, allowing the signal to travel longer distances without fading. (The process of an electrical signal gradually fading in strength over distance is "attenuation".) A hub is basically a multiport repeater, and both of these devices are considered Physical layer devices. Ethernet and Token Ring both operate at the Physical layer as well.

Learning the OSI model's Physical layer isn't just important in your CCNA exam studies, it's the first step in any network troubleshooting. After all, your network's end users are going to have a tough time sending print jobs to a printer that's turned off!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.

For a FREE copy of his latest e-books, ?How To Pass The CCNA? and ?How To Pass The CCNP?, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Pass the CCNA exam with The Bryant Advantage! thebryantadvantage.comchris@thebryantadvantage.com

 

Cisco CCNP / BSCI Tutorial: Comparing OSPF And ISIS Hellos

While studying to pass the BSCI exam and preparing to earn your CCNP certification, you'll quickly notice that while OSPF and ISIS are both link-state protocols, there are a lot of differences between the two. One major difference is the way the two protocols handle hello packets.

Hello packets are imperative to keeping OSPF and ISIS adjacencies alive. Since they are both link-state protocols, neither of them will send updates at any specified time. Hello packets are the only method by which routers running OSPF and ISIS can see that a neighboring router is still available.

OSPF gives us some great options when it comes to keeping routing table size down via the use of stub and total stub areas, but to OSPF, a hello packet is a hello packet. ISIS routers are capable of sending two different types of hellos - Level 1 and Level 2.

ISIS routers are classified as Level 1 (L1), Level 2 (L2), and Level 1-2 (L1-L2). By default, Cisco routers are L1-L2 routers; this means that every ISIS-enabled interface will send out both L1 and L2 hellos.

If one of the interfaces is forming only an L1 or L2 adjacency, there's no reason to send out hellos for the other adjacency type. For example, if R1 is forming an L1 adjacency with R2 via its ethernet0 interface, there is no reason to allow the router to transmit L2 hellos. To hardcode a router interface to send only L1 or L2 hellos, use the isis circuit-type command.

R1(config)#interface ethernet0

R1(config-if)#isis circuit-type level-1

Note: To configure this interface to send only L2 hellos, the full command is "isis circuit-type level-2-only", not just "level-2".

This configuration would prevent L2 hellos from being transmitted out ethernet0. While this does save router resources and prevents unnecessary bandwidth usage, there is also no way an L2 adjacency can be formed - so double-check your network topology before using this command!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Earn your CCNA certification with The Bryant Advantage!

Cisco CCNA/CCNP Home Lab Setup: How To Configure Reverse Telnet

Occasionally, during your CCNA and CCNP studies, you'll run into a term that just doesn't quite make sense to you. (Okay, more than occasionally!) One such term is "reverse telnet". As a Cisco certification candidate, you know that telnet is simply a protocol that allows you to remotely connect to a networking device such as a router or switch. But what is "reverse telnet", and why is it so important to a Cisco CCNA / CCNP home lab setup?

Where a telnet session is started by a remote user who wants to remotely control a router or switch, a reverse telnet session is started when the host device itself imitates the telnet session.

In a CCNA / CCNP home lab, reverse telnet is configured and used on the access server. The access server isn't a white box server like most of us are used to; an access server is a Cisco router that allows you to connect to multiple routers and switches with one session without having to move a rollover cable from device to device.

Your access server will use an octal cable to connect to the other routers and switches in your home lab. The octal cable has one large serial connector that will connect to the access server, and eight rj-45 connectors that will connect to your other home lab devices. Your access server then needs an IP Host table in order to perform reverse telnet.

An IP Host table is easy to put together (and you better know how to write one to pass the CCNA!). The IP Host table is used for local name resolution, taking the place of a DNS server. A typical access server IP Host table looks like this:

ip host FRS 2007 100.1.1.1

ip host R3 2003 100.1.1.1

ip host R1 2001 100.1.1.1

ip host R2 2002 100.1.1.1

ip host R4 2004 100.1.1.1

ip host R5 2005 100.1.1.1

ip host SW1 2006 100.1.1.1

interface Loopback0

ip address 100.1.1.1 255.255.255.255

no ip directed-broadcast

This configuration will allow you to use your access server to connect to five routers, a frame relay switch, and a switch without ever moving a cable. When you type "R1" at the console line, for example, you'll be connected to R1 via reverse telnet. If you have a smaller lab, an access server is still a real timesaver and an excellent investment. And by getting a static IP address to put on your access server, you can even connect to your home lab from remote locations!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com ), home of free CCNA and CCNP tutorials, and The Ultimate CCNA and CCNP Study Packages. For a copy of his FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies!